I offer this for consideration. I recently started to change out the fluid and discovered the following:
1) The reservoir had some sludge in the bottom probably from moisture. The clutch was working.
2) When attempting to change and bleed the system, all of a sudden the lever had no resistance for most of the travel. I discovered the master cylinder return spring was broken into 4 pcs.! Was weird because the clutch operated before I started the fluid change???
Good Luck.
Yep, this type of thing can happen with any hydraulic system when bleeding, as things have to stroke much further than in normal service, sometimes ruining seals, springs, etc. Got to be extra careful bleeding, and even at that sometimes stuff just fails.